Country star Garth Brooks is trying to hide a family secret from his fans - his sister Betsy Smittle is allegedly struggling with bipolar disorder and recently faced police arrest for streaking down her street.

Smittle, who performed alongside her little brother from 1989 to 1995, is still close with Brooks and he reportedly rushed to her Tulsa, Oklahoma home on 26 April (09) when he learned she was acting strangely.

According to America's Globe publication, Smittle, whose birth name is Harriet, suffered a mini-breakdown after a fight with her gay lover and ran out of the home they share naked.

Police confirm they were called to the scene by concerned neighbours, who feared Smittle was suicidal.

A spokesman tells the publication, "She didn't exhibit any signs she was a danger to herself or others," and the authorities made no arrest.

According to the Globe, Smittle was hospitalised following the naked escapade. She underwent two weeks of psychiatric care and then readmitted herself to hospital after failing to resolve issues with her partner.

A friend tells the publication, "She (Smittle) told me they had trouble finding the right meds (medication) for her." (c) WENN